Several AS3 changes

- Parsing of configuration files defined in the project properties.
- Dot is valid in tag names. Solves autocompletion in MXML child
attributes with states.
- Used the outline to get the parent tag data in MXML, solves a FD issue
with old method, and is faster.
- Some MXML parsing improvements.
- More accurate GoToDeclaration support. Added support for going to the
declaration of meta tag attributes and states.
- Moved MetaData from FileModel to ClassModel, more accurate, eases some
cases, and will allow  supporting and improving several cases easily.
- WIP: MetaData completion (descriptor XML not committed either yet).
Hope I can resume work on it soon.
Misc MXML autocompletion improvements

- Namespace declaration autocompletion.
- Fixed attribute value autocompletion when state is defined.
- Added state autocompletion for attributes defined on secondary nodes.
Dot completion for namespaces
Improved interface implementation generator

Detect correctly the implements attribute value is selected, and get the
right interface down the cursor.
More concise MXML auto-completion.
Improved metadata parsing.
Write meta tags intrinsic even if of unknown type.
Support for DefaultProperty meta tag.
Support for ArrayElementType meta tag.
Support for InstanceType meta tag.

NOTE: Work preliminar, as it's missing showing proper special fx/mx tags depending of context, and getting inheritance chain is rather slow. I need to think of some cache mechanism for this.