* sk.po
Rename misleading parameter.

... and a typo and some whitespace.
Centralize replacement of "$$s"

Now the replacement is done in startScript(). In addition to making
the code cleaner and more consistent, this commit fixes a bug where
"$$s" was not replaced when "latex=" was specified in the extra flags
of a converter.

Note that the temporary fix at 731b8610 is reverted with this commit.
Centralize substitution of python commands

The code for detecting python commands and substituting in the
correct prefix is now merged with what used to be libScriptSearch()
and is now renamed to commandPrep(). This commit does not change
any functionality and just improves organization to reduce the
chance of bugs in the future.
Output a parbreak after a command.

This is what LyX was previously doing. It has no effect on vertical
spacing but, for example, sectioning commands stand out on the output.
The parbreak is not output if an environment follows or the alignment
of the current or next paragraph is changed.
Also remove some superfluous code.