PicSphere: First batch of enhancements [2/2]

This patch:
- Enable the building of cpfind, multiblend, pto_gen
  and pto_var
- Add linefind and multiblend source
- Add a popen JNI helper
- Remove lots of debugging messages
- Remove hacks of what was supposed to be the
  source of freezes

Change-Id: I3c26bfe5a51dd26fc9aaa77bb7c1c2655101689b