Fixed an issue with syntax coloring when unicode characters are present in the text editor.

The python files parse.py and python.py now convert the string input from C code to unicode strings.
Several improvements to window launching.

Tabs are now added before the window appears.
Resolved an issue where the text editor was not first responder on application launch. This fix adds PLWindow, a NSWindow subclass that forwards first responder status to its controller.
Windows are not set to "visible on launch" in their xib files. This resolves an issue where the window appears before being cascaded.
Improved window titles.

Main window titles are set to the filename of the document and given a represented URL (this provides builtin path information when cmd-clicking the title).
The credit window now has a title: About Liasis.
Changed PLTabSubviewController document method to return a PLDocument <PLDocumentSubclass> as this makes it more clear to get the filename and URL in PLTabViewController for setting the window title.
Added key equivalents to the main menu bar for switching tabs.

Added public methods to PLWindowController for LiasisAppDelegate to forward the key equivalents to.
Opening windows by double clicking files now adds a tab to an existing window if available.
Added fullscreen support.