Allow tables in arbitrarily deep hdf5 groups

[kosack]

This is a change to HDF5TableWriter to allow tables to be output to arbitrarily deep groups in an HDF5 file.

The main change (other than some reformatting) is:

• the group_name attribute of the HDF5TableWriter is now considered the "base" group (from which all sub-tables will be under)
• writer.write(table_name="x", containers=y) works as before, but now you can add deeper nesting like writer.write(table_name="subgroup/anothergroup/x", containers=y) and subgroup and anothergroup will be created automatically if they don't exist.
• the unit test test_write_to_any_location has been re-enabled (it was marked as xfail before)

A full example:

with HDF5TableWriter("output.h5", group_name="/dl1/tel") as writer:
    for event in source:
         ...
         writer.write("image/NectarCam", somedata) 
         writer.write("params", paramdata)

Would create 2 tables: /dl1/tel/image/NectarCam and /dl1/tel/params

This allow a nicer structure, as shown in #1059 (v5 and above)

[codecov]

Codecov Report

Merging #1068 into master will increase coverage by 0.05%.
The diff coverage is 98.75%.

@@            Coverage Diff             @@
##           master    #1068      +/-   ##
==========================================
+ Coverage   83.44%   83.49%   +0.05%     
==========================================
  Files         181      181              
  Lines       10439    10448       +9     
==========================================
+ Hits         8711     8724      +13     
+ Misses       1728     1724       -4

Impacted Files	Coverage Δ
ctapipe/io/tests/test_hdf5.py	97.24% <100%> (+2.38%)	⬆️
ctapipe/io/hdf5tableio.py	93.49% <88.88%> (-0.42%)	⬇️

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update fea8a57...f7f6789. Read the comment docs.

[vuillaut]

Definitely something we want.

[kosack]

I think this is ready to go - codacy complains a bit about some test variable names, but I think those can be ignored for now.