Less verbose find_ends

[IceFreez3r]

Was looking into the code to find out how Mandalorion determines TSS/TES and couldn't resist optimizing this function. Code logic should be exactly the same.

Changes:

• Less indentation using inverted if's with continue
• dict.get with default value to remove checks
• Compress for-loops into one-liners
• More efficient use of range and np.arange
  • range for iteration, arange for arrays that get used, see also here: https://stackoverflow.com/a/10709601/12540220
• spaces around assignment operators
• moved magic number 10 to constant
• removed unused variables

Apart from the PR, is there any place where I can find the thoughts for your strategy of determining TSS and TES?