Bugfix for RANSAC outlier detection; fastened RANSAC parameter optimization; added maximum points parameter

components.CoReg_local.COREG_LOCAL:
- __init__():
    - added new keyword 'max_points' for setting maximum number points to which co-registration algorithm is applied
    - revised docstring
- view_CoRegPoints(): removed dirty hack from last commit

components.Geom_Quality_Grid.Geom_Quality_Grid:
- __init__():
    - added new keyword 'max_points' for setting maximum number points to which co-registration algorithm is applied
    - revised docstring
- _get_imXY__mapXY_points(): added docstring
- added function _exclude_bad_XYpos()
- get_CoRegPoints_table():
     - removed keyword 'exclude_outliers' (makes no sense anymore)
     - moved exclusion of bad data points to new function _exclude_bad_XYpos()
     - added random point selection in case maximum number of points has been provided

components.Geom_Quality_Grid.Tie_Point_Refiner:
- results of RANSAC filtering are now correctly merged to rest of the point cloud
- revised _RANSAC_outlier_detection(): fastened parameter optimization

- updated __version__