Add mesh_stats and field_operations

[alexbenedicto]

Following the work of @ryar9534 with PR #19 where he started to implement two distincts features:

• add_fields which allowed for the transfer of data properties from an input mesh to an output mesh
• mesh_stats which gave a summary of mesh statistics

These features have been further developed and reworked ( add_fields became field_operations ) and should validate the tasks for checks in GEOS-DEV/GEOS#2270.