Introduces:
- class for Picard--Fuchs operators and their ideals
- class for periods (their complex linear combinations in the Frobenius bases)
Implements:
- method to obtain operator from period
- method to get power series solution (at given indicials) to PF ideal
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Co-authored-by: Julian Piribauer <julian.piribauer@gmail.com>
Reviewed-on: #13
