Expand role of syntax sections beyond colors

[pgengler]

In addition to the current role of coloration, the "syntax" sections should also be able to specify/override options that should be set for files of that type.

For example, a "YAML" syntax block could set "tabstospaces" (since tabs are invalid in YAML files) while leaving other file types unaffected.

"tabsize" is another good candidate for being overrideable on a per-syntax basis