The option here is to NOT indent the paragraph, so make that clear.
As it was, we would set "Indent" to false in the case of paragraphs
that do not permit indentation and then write that, uselessly, to the
LyX file if we wrote any other option (and then keep writing it, even
if other options were removed). Now, we will write it only if it's been
explicitly set.
In particular, the directory frontends/qt4 is renamed to frontends/qt.
Many configurations file have to be updated. All mentions of qt4 in
the source have been audited, and changed to qt if necessary.
The only part that has not been updated is the CMake build system.
