Move LSL keyword default to lsl_definitions.yaml

[tapple]

default was misplaced in the keywords file as a constant, rather than a control, and the generators had some special handling for it. Move it to the logical place, and remove the exceptions

This also removes exceptional handling for it in the unmerged textmate generator: #120 (review)

This changes it's in-viewer highlighting color from blue to purple

[HaroldCindy]

It's really only under there so the color of default is distinct from state foo. Is having it in constants breaking anything?

[tapple]

it's not breaking anything, in that:

1. it's been this way since time immemorial
2. it's only one item in the wrong place and thus is easy to single out an exception for.

Why somebody wanted it to have a different color than state foo, I have no idea (I would prefer they matched), but, that's the only theory present in the code.

The motivation for this PR is indeed weak: removing a one-line exception from the textmate generator, and 7 lines of exception elsewhere

While I don't have a strong opinion about the highlighting color (bikeshed topic), it would be nice to move default's description source from lsl.py to lsl_definitions.yaml (this would also get rid of the textmate exception). I could still put it in with the constants in the keywords.xml generator, to preserve the color

[WolfGangS]

Personally i agree it should be in flow control.

But i do think it needs a special case to be kept in constants for now for keywords.xml changing that after so many years is probably not advisable.

I'm pretty certain that loads of less familiar scripters would think its an error or just miss it being blue 😢

[tapple]

moved it back to constants in keywords.xml: a959614. Now this PR no longer changes keywords.xml