Nxquadric 1

[tcspain]

Proposed NXquadric and NXcsg classes to allow the definition of constructive solid geometry from quadric surfaces.

[zjttoefs]

That build failed, please fix the tags.

[prjemian]

Please remove the example data from this PR. You are encouraged to make a companion PR in the NeXus repository for example data: https://github.com/nexusformat/exampledata

You may need to create a subdirectory path for this. Try to follow the apparent practice. Add a README.md with the example data to describe the file(s) such as what it is and whether or not the files are compliant with the NeXus standard (version ____).

[prjemian]

The failure is in the XML:

======================================================================
ERROR: test__3__contributed_definitions__NXcsg (test_nxdl.Individual_NXDL_Tests)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/home/travis/build/nexusformat/definitions/utils/test_nxdl.py", line 90, in test_wrap
    validate_xml(nxdl_file_name)
  File "/home/travis/build/nexusformat/definitions/utils/test_nxdl.py", line 54, in validate_xml
    raise NXDL_Invalid(msg)
NXDL_Invalid: contributed_definitions/NXcsg.nxdl.xml : error parsing attribute name, line 38, column 5 (line 38)
======================================================================
ERROR: test__3__contributed_definitions__NXquadric (test_nxdl.Individual_NXDL_Tests)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/home/travis/build/nexusformat/definitions/utils/test_nxdl.py", line 90, in test_wrap
    validate_xml(nxdl_file_name)
  File "/home/travis/build/nexusformat/definitions/utils/test_nxdl.py", line 54, in validate_xml
    raise NXDL_Invalid(msg)
NXDL_Invalid: contributed_definitions/NXquadric.nxdl.xml : Opening and ending tag mismatch: field line 49 and definition, line 87, column 14 (line 87)

1. In NXcsg.nxdl.xml, line 37, you are missing the closing >
2. In NXquadric.nxdl.xml, after line 76 (before line 77), you are missing the closing </field> that opened on line 49.
3. In NXquadric.nxdl.xml, line 50, the field name type could be more specific in my opinion. Since type is common in XML files and other contexts, confusion of this generic name with some other concept is possible.

[prjemian]

commented previously, changes made, passes travis-ci validation checks, ok. Thanks!

[prjemian]

Comments by anyone else? Shall we merge? Marking for next telco.