Removed restriction of one reference pull group

The pull code now uses separate pull groups and coordinates,
which removes any restriction on group pairing.
The pull geometry "position" has been removed, but the origin
option replaces this functionaliy in case of an absolute reference.
Removed triple use of the init option.
Refs #1346

Change-Id: I90736ac6b6f18e3bf26a344072172a69627566e9
Fix test build with GMX_BUILD_MDRUN_ONLY

Removed the tests from such builds to resolve CMake errors.
The tests cannot in any case be run without non-mdrun code.
Got broken in I8072355.

Also moved the object library for gmx view such that it doesn't get
unnecessary built with GMX_BUILD_MDRUN_ONLY.

Change-Id: I52c19d695680f5bd94deaae712d2d10e3364dfa6
Fix administrivia

Added install guide section for mdrun-only builds and testing same

Change-Id: I3b7c1cf6fec7c96fe162d4d6362bebd2128ac288
Version bump after 5.0-beta1 release

Change-Id: Iedcf90669847e2c02ac5a17dd799245930075b28
Merge branch 'master' into comp_el_master
CompEl: Removed 'auto' option that was not implemented yet