Add UI to provide args for templates, to enable template IntelliSense

[rdlaner]

* Operating System and version

MacOS 10.13.4

* VS Code version and if you are using the Insiders build

VSCode 1.24.0-Insiders #2404210629c744e6237a14d7b5fa852e24c6e898

* C/C++ extension version

0.16.1

* step-by-step instructions to reproduce the issue

Create at least one class declaration in a header file. Use a template on this class Intentionally create a syntax error Note that no error squiggles are generated and no error or warning given in the Problems pane. In the example below, I am showing quite a few compiler errors (there are plenty in this file). One in particular is the errant use of override. This shows up in the compiler output, but not in the error squiggles or in the Problems pane:

* A small code sample, zipped up project, or open source repo we can use to verify the bug

Errant header file attached LinkedList.h.zip

* Any log messages present in the Output window (use "C_Cpp.loggingLevel": "Information" in settings.json)

The logs indicate that it thinks it is looking for syntax errors: IntelliSense Engine = Default. The extension will use the Tag Parser for IntelliSense when #includes don't resolve. Autocomplete is enabled. Error squiggles are enabled. File exclude: **/.git File exclude: **/.svn File exclude: **/.hg File exclude: **/CVS File exclude: **/.DS_Store File exclude: **/.o File exclude: **/.d File exclude: **/.vscode Search exclude: **/node_modules Search exclude: **/bower_components Search exclude: **/.vscode Code browsing service initialized Folder: /usr/local/include/ will be indexed Folder: /usr/local/Cellar/gcc/7.3.0_1/include/c++/7.3.0/ will be indexed Folder: /Users/dustinlane/Desktop/VSCode_Test/ will be indexed Folder: /System/Library/Frameworks/ will be indexed Folder: /Library/Frameworks/ will be indexed Discovering files... Checking for syntax errors: file:///Users/dustinlane/Desktop/VSCode_Test/C%2B%2B_Test/LinkedList.h Processing folder (recursive): /usr/local/include/ Processing folder (recursive): /usr/local/Cellar/gcc/7.3.0_1/include/c++/7.3.0/ Processing folder (recursive): /Users/dustinlane/Desktop/VSCode_Test/ Processing folder (recursive): /System/Library/Frameworks/ Checking for syntax errors: file:///Users/dustinlane/Desktop/VSCode_Test/C%2B%2B_Test/LinkedList.h Checking for syntax errors: file:///Users/dustinlane/Desktop/VSCode_Test/C%2B%2B_Test/LinkedList.h Checking for syntax errors: file:///Users/dustinlane/Desktop/VSCode_Test/C%2B%2B_Test/LinkedList.cpp Shutting down IntelliSense server: /Users/dustinlane/Desktop/VSCode_Test/C++_Test/main.cpp Checking for syntax errors: file:///Users/dustinlane/Desktop/VSCode_Test/C%2B%2B_Test/LinkedList.h Checking for syntax errors: file:///Users/dustinlane/Desktop/VSCode_Test/C%2B%2B_Test/LinkedList.h Processing folder (recursive): /Library/Frameworks/ Discovering files: 301712 file(s) processed 0 file(s) removed from database Done discovering files. Parsing open files... Parsing remaining files... Parsing: 0 files(s) processed Done parsing remaining files. Done parsing open files. Checking for syntax errors: file:///Users/dustinlane/Desktop/VSCode_Test/C%2B%2B_Test/main.cpp Checking for syntax errors: file:///Users/dustinlane/Desktop/VSCode_Test/C%2B%2B_Test/LinkedList.h