Adding del_feed to the feedhandler class

[spc789]

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Case scenario : suppose one wants to follow only the feeds which are - for example - above a 24u volume, or where the volatility is above a specific thresshold.
Every day at some time the feeds/coinpairs which are needed are re-calculated.
It could happen some feeds which were needed the day before are not needed after the recalculation.
To preserve speed a function which deletes those "old", unnecessary feeds, is necessary.

Describe the solution you'd like
A del_feed analogy as in add_feed function in the class could solve this problem.

Describe alternatives you've considered
The alternative is could be restarting the whole feed program with the correct pairs from that moment, leaving slightly gaps in some data. Ie in the pairs which are not changed