update MuSEEK to protect point sources (in aoflagger), mask(in gain calibration) and recover (after gain calibration)

[mariogrs]

Given the new point source catalog in #87 (all sources in the catalogue currently have flux > 5 Jy):

• Write a general "utility" function that read a source catalogue and select sources in the cataloge given a flux threshold
• Write a function that take a ToD and a list of point sources and return point source flags for the ToD
• Update the AOFlgger plugins to take a flux threshold that get passed to the above utility functions, and then mask relevant point sources during the flagging. The threshold should be one of the parameter of the plugin
• Update part of the code that does the gain calibration with the Synchrotron model to also use the point source flags.

[mariogrs]

Is this done?

[kfornaz]

@wkhu-astro checked, update the catalog.

[kfornaz]

@wkhu-astro wrote in the ([https://github.com/meerklass/museek/blob/gain-calibration/museek/util/tools.py]) a function ( point_sources_coordinate(point_source_file_path, point_sources_match_flux) ) which reads a source catalogue and select sources in the catalog given a flux threshold. Also wrote in the same tool.py another function, point_source_flag(ra_point_source, dec_point_source, ra_scan, dec_scan, frequency, beam_threshold, beamsize, beam_frequency), which returns TOD mask for point sources
@wkhu-astro finished updating the Museek, the point source masking module is ready. @kfornaz is testing as described in #89