Recurrence matrices have dedicated structs now

[WIP] Dedicated structs for recurrence matrices (#25)

* export Dataset as well, seems useful.

* recurrence matrix type and its pretty printing

* change function return types

* each matrix gets its own type.

* more necessary method propagation

* more elegant method propagation

* update recurrence rate

* enforce as constant that RecurrenceMatrix is symmetric

* correct mistake: Int instead of Int64

* replace all dispatches with ARM

and comment out windowed for now.

* use new types in tests

* update plotting to new types

* remove `AbstractMatrix` methods for diagonal and vertical histograms

* extend iterate

and uncomment windowed

* type stability in trend and recurrencerate

* fix windowed with JointRecurrenceMatrix

* change field from .m to .data

* fix windowed rqa functions

* change gensym by local variable declarations in windowed

* added documentation and comments on windowed

* delete "=  true" in pretty printing of recurrence matrices (#27)

* docstring fixes

* deprecations