Compiler updates

The following changes are included:

* JS files are not put into the current working directory of the compiler but next to the Smalltalk source file (e.g. `project/Test/Package.st` now produces `project/Test/Package.js` instead of `./Package.js`)
* an output directory can be specified into which all JS files get generated (`-D` for commandline version, `output_dir` variable for grunt version). This overwrites previous behavior.
* adding minification flags now implies deploy mode
* minified sources are used to generate program files in deploy mode to get smaller executables