Format python files according to PEP-8
Remove unused classes

Reformat xml files.
Clean up AST

nesc-ast module:
 * remove CString (use java.lang.String instead)
 * remove unused classes
 * modify ast node definitions for nesc extensions
   - add endLocation attribute to AST Node
   - rename attributes (e.g. word1 -> alias)
 * add new ast nodes (makes ast structure less confusing)

nesc-frontend module:
 * each parser token contains start and end location
 * negative numbers (consecutive minus and number token occurrences)
   are no longer considered by preprocessor as a single token (there
   is no need to handle this case)
 * simplify building AST in bison grammar (nesc extensions)
Fix preprocessor directive base class

- add missing getter
Collect tokens that should be coloured in plugin

Only keywords, constants, punctuation marks are collected so far.
Keywords are kept in multimap, where the key is a line number and
the value is a collection of tokens in the line.

Log both to file and to console.
Frontend returns errors multimap

Errors and warnings are collected into multimap separately for each
file.
Returned errors:
 - syntax errors
 - interface/component file cannot be found