Add check_duplicates method to Endpoint

[Ajstros]

This method allows us to check for and view the names of duplicate Endpoints. These are not necessarily wrong, because there are cases where you might refer to the same Endpoint by multiple names, or in different groups, but they are good to know about.

[Ajstros]

Example usage:

>>> from pyripherals.core import Endpoint
>>> _ = Endpoint.update_endpoints_from_defines()
>>> dups = Endpoint.check_duplicates()
5 duplicate Endpoints found.
0x0[None:None]
         ADS8686/REGBRIDGE_OFFSET
         GPIO/DEBUG_WIRE_IN
0x3[3:6]
         DAC80508/DATA_SEL_LEN
         AD5453/DATA_SEL
         AD5453/DATA_SEL_LEN
         AD5453/DATA_SEL_LEN
0x11[1:2]
         DAC80508/FILTER_SEL_LEN
         AD5453/FILTER_SEL_LEN
0x0[3:6]
         GPIO/CSB_DEBUG_LEN
         GPIO/SCLK_DEBUG
         GPIO/SCLK_DEBUG_LEN
         GPIO/SDI_DEBUG_LEN
         GPIO/ADS_CONVST_DEBUG_LEN
         GPIO/SCLK_DEBUG_LEN
         GPIO/SDI_DEBUG_LEN
         GPIO/ADS_CONVST_DEBUG_LEN
         GPIO/SDI_DEBUG_LEN
         GPIO/ADS_CONVST_DEBUG_LEN
         GPIO/ADS_CONVST_DEBUG_LEN
0x1[6:7]
         GPIO/UP_WIRE_IN_LEN
         GPIO/DOWN_WIRE_IN_LEN
         GPIO/3V3_WIRE_IN_LEN
         GPIO/3V3_WIRE_IN_LEN