Linux support.

[damellis]

We need various libraries.

ESP

GRT

Options:

1. ~~Compile as a static library and link into ESP library.~~
2. ~~Compile as a static library and distribute with the Processing mode.~~ (This is probably also a good option.)
3. Compile as a shared library and distribute with the Processing mode. This may require some linker magic with rpath / LD_RUN_PATH so that the eventual ESP executables can find the library.
4. ~~Compile as a shared library and make the user of the Processing mode install it.~~ (This seems like unnecessary extra work for the user.)

openFrameworks

Options:

1. Distribute the static library in the ESP mode.
2. ~~Link the openFrameworks static library into the ESP static library.~~
3. ~~Don't distribute anything and have the mode compile openFrameworks on the user's machine when you first install it.~~ (Maybe Later)

openFrameworks dependencies (system packages)

Options:

1. Have the user run the install script from the version of openFrameworks included in the mode.
2. ~~Provide standalone instructions and/or scripts for installing the required packages.~~ (This won't handle recompilation of the Poco libraries, which is something required and done by install_dependencies.sh.)
3. Automatically run the install script from the included openFrameworks when the mode is first installed.