Replaced the custom bracket highlighting in PLEditorViewController with the builtin NSTextView find indicator.

Uses the showFindIndicatorForRange: method of NSTextView instead of the layer instance variable with custom animation. Changed the name of the animateCharacter:atPosition: method to animateBracketInTextView:matchingPosition: for improved clarity.
Made changes to the add on manager, document manager and the file browser in order to open a new tab with the default view extension for each document type.

These changes involve adding Info plist dictionaries that specify each bundle's allowed document type, its corresponding document class, and adding a defaults dictionary that contains default view extensions for each allowable file type.
Modified the open file dialog to register all allowed file types for all the loaded add ons.
Modified the app delegate openFile: method to allow for multiple open files at a single time.
Fixed an issue that was appearing with a third party view extension that was causing Liasis to crash when closing the last tab view.
Xcode project set to use 10.8 as base SDK.
Improved retrieving node titles when parsing for navigation items.

Instead of determining each argument in a function/class definition, the new approach simply gets the first line of a definition from the source string.
Reduced size of navigation item images for improved performance.
Fixed an issue when opening documents that caused the program to quit if opening a file was canceled. Added the setBookmarkData: method in the abstract document class to allow for the document manager to change the bookmark data for a given document.
Merge branch 'develop' into feature-documents