Clean the graph connection

See merge request !103

rename `scope->idx_scope`, `idx->idx_input`, `idx_out->idx_output` in the input strategies, move input strategy for `ViewConcat` node to the common file for them (`input_strategy.py`); small fixes

rename `SimpleFormatter -> SimpleLimbNameFormatter` and `SequentialFormatter -> SequentialLimbNameFormatter`; fix wording; update type hinting (add `Generator`); fix exception message

slightly improve `input_strategy` setter in the NodeBase: add comments, rename argument to `new_input_strategy`; fix meaning error in exception in the connection methods: `not implemented` to `not supported`

rename `Formatter -> LimbNameFormatter`, adding description of the reimplementation of the connection method in the CovarianceMatrixGroup; fix a mistake `nethod -> method`

rename `MissingInputStrategy -> InheritInputStrategy` and move into `core.input_strategy.py`; clean `<<` operator for `NodeBase`; other small fixes

improve connection of MetaNodes: now it is possible to reimplement custom behaviour like it is done for CovarianceMatrixGroup

fix bug of connection of `Sequence[Node] >> Node`, where lhs is a sequence of nodes with 1 output (allowed connection): previously such connection creates a new output for each node in the sequence, which is generally wrong behaviour, for instance, for BlockToOneNode; improve the test

Add Profiling module: the way to estimate time of nodes and framework overhead

See merge request !60

this prevents from using positional args, making the code less
error-prone