Updated and cleaned-up clippings

This pull request kind of looks like major surgery, but it’s built on enhancing the BBEdit clippings clippings with, er, clippings. All of the clippings that took a label (`*PLACEHOLDER*`) or parameter (`SCRIPT`, `DATE`, etc) now include a `SELECTIONOR(INSERTION|PLACEHOLDER)` to make it easier to add them.

I’ve added a plain placeholder (`<#…#>`), an optional-argument one (`<#*…#>`), and enhanced the optional placeholder (`<#?…#>`) as described above.

The XXX & YYY suffixes have been chopped from the date and time clippings since they’re just referring to the format strings that are required for use anyway. GMTIME now works.

Lastly I’ve removed the initial `#INDENT#` from all of the clippings since they’re all single-line and therefore not affected.