Update Ubuntu build docs [1/1]


Moves Ubuntu specific instruction to dev-vm-Ubuntu.md, and makes
devtool-build.md generic, with pointers to OS specific instructions.



 doc/devguide/development/dev-vm-Ubuntu.md | 138 +++++++++++++++--------
 doc/devguide/devtool-build.md             | 175 ++++++++++++++----------------
 2 files changed, 173 insertions(+), 140 deletions(-)

Crowbar-Pull-ID: a8c24050b747a2fc9f7d9211ac7ba602c7535abe

Crowbar-Release: development