modules: add find, load and reload core functions

[sebastien]

K7 should offer primitive for accessing and manipulating modules (in plain C++):

• find(moduleName): finds the .js or .so representing the module in one of the K7_PATH dirs
• load(modulePath): loads the .js or .so module at the given location
• reload(modulePath): reloads the .js or .so module at the given location