Missing docstring and minor errors in documentation

[albinahlback]

Scrolling through the documentation for Hecke I saw some minor errors.

For example, at https://www.thofma.com/Hecke.jl/dev/orders/orders/ there is a missing docstring for denominator and a \Z at the first docstring (should probably be \mathbf{Z}).

[albinahlback]

Also the "Source" hyperref does not link anywhere. It opens a tab which contain a link under the name "None".

[albinahlback]

The long equation has a greater width than the text does. In some cases (but not the one shown here) it causes a cut-off at the end.

[albinahlback]

Missing docstring for maximal_order(::AnticNumberField, ::Array{fmpz, 1}).

[albinahlback]

There are some missing in docstrings in /Order, but I can't seem to find out why some of them behave that way. For example, I think class_group should be well-behaved, but it's missing.