[On Hold] add SHSignal to docs

[tluebeck]

Which issue(s) are closed by this pull request?

Closes #

Changes proposed in this pull request:

• added SphericalHarmonicSignal to documentation, similar to pyfar style
• added introduction to SpamplingSphere documentation page
• we need to wait for Add Spherical Harmonics class #101 to add a general documentation of the Spherical Harmonics implementation

[ahms5]

maybe we can also discuss if we want to have it on one doc page or each class on separated doc pages.

[f-brinkmann]

@tluebeck I opened #152 would suggest the following after merging this:

• Lets make an entry 'Spherical Harmonic' under the Classes section of the docs
• This entry contains the SphericalHarmonic class and the SHSignal
• Move the general documentation that is now in the SphericalHarmonic class to the top of the docs page
• add information which combinations of parameters result in poular SH conventions (AmbiX, Willians/Rafely, Arend/Spors, SOFA, MPEG)

[tluebeck]

As discussed in #160 we can consider moving SHSignal to classes.sh as well and include the documentation at the top of that file. Let's discuss tomorrow.

[mberz]

Please remove the _build directory from git ;)

[ahms5]

this pr is partially v1.0.0 and v1.1.0 we need to fix it somehow @mberz @tluebeck

[f-brinkmann]

this pr is partially v1.0.0 and v1.1.0 we need to fix it somehow @mberz @tluebeck

Also see #176

[sikersten]

Also relevant for #173

[mberz]

Since this PR tries to do too many things at once (and also does not agree with the new release schedule), I'll split it up into smaller PRs over the next days and subsequently close here.
For this reason I'm moving this PR to "on hold" and revoke all reviews and assignees.