perf scripts python: exported-sql-viewer.py: Add 'About' dialog box

perf scripts python: exported-sql-viewer.py: Add 'About' dialog box

With support for Python 2 or 3 and PySide 1 or 2 (Qt 4 or 5), it is
useful to see what versions are in use. Add an 'About' dialog box that
displays Python, PySide, Qt and database server (SQLite or PostgreSQL)
version numbers.

Committer testing:

  $ python ~acme/libexec/perf-core/scripts/python/exported-sql-viewer.py ~/c/adrian.hunter/simple-retpoline.db

  Then go to 'Help', then 'About', select all the lines with the mouse
  press 'Control+C', then, on the same terminal press control+shift+V
  which shows my current environment:

Python version:     2.7.16
PySide version:     1
Qt version:         4.8.7
SQLite version:     3.26.0

Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Link: http://lkml.kernel.org/r/20190503120828.25326-7-adrian.hunter@intel.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>