Fix initialization order of MANTIDLIBS cmake variable.

If MPI is enabled then this ensures the Boost_LIBRARIES variable is
captured before it is overwritten.
Refs #10632
Refs #10686. fix warnings in Mantid and tests
Refs #10686. fixed misspelled header guard.
Refs #10686. fixed unused-parameter warning on gcc.
Merge remote-tracking branch 'origin/feature/9915_add_usage_example_sinq_focus'
Merge remote-tracking branch 'origin/bugfix/10675_idr_et_use_saveascii_v1'
Use RelWithDbgInfo as default build type for build servers

Refs #10690
Merge remote-tracking branch 'origin/feature/7938_improve_script_editor'
Merge remote-tracking branch 'origin/feature/10512_link_idf_options_to_ui'
Merge remote-tracking branch 'origin/feature/10687_indirect_diffraction_ungroup_result_workspaces'
Merge remote-tracking branch 'origin/feature/10170_loadvesuvio_sum_multiple_spectra'
Merge remote-tracking branch 'origin/feature/10666_Improve_first_time_dialog'
Merge remote-tracking branch 'origin/bugfix/9468_sort_table'
Merge pull request #83 from mantidproject/feature/10686_fix_Wall_warnings

fix -Wall warnings on OS X with AppleClang
Merge remote-tracking branch 'origin/feature/10674_crash_loading_matrix'
Merge remote-tracking branch 'origin/feature/10623_enable_poldi_2d_fitting'
Re #10498 merging branches
Merge pull request #84 from mantidproject/feature/10690_relwithdbg_package_builds

Use RelWithDbgInfo as default build type for build servers
Merge remote-tracking branch 'origin/feature/10642_absolute_getdetectoroffsets'
Merge remote-tracking branch 'origin/feature/10359_eventfilter_gui_reset'