hotfix connector shapes have no adjustments
hotfix: add customXml part types
Document initial analysis for document properties
Presentation has core properties

Note: reordered 'I have an empty presentation open' step
Reformat comments in test_presentation.py
_RelationshipCollection can find related part
Reformat comments in test_oxml.py
Implement _CoreProperties.title property
Add subject and author core doc props

* Generalize oxml tests
* Generalize CT_CorePropertiesBuilder
Generalize oxml access to string docprops
reformat incidental lab files to PEP8
generalize string core prop access
implement first date core prop
generalize date core prop access
implement _CoreProperties.revision property
add default core props part when not one in pkg

On open of package having no /docProps/core.xml part, create and add
one containing a minimal set of properties set to default values.
complete coreprops doc and refactoring
Merge feature 'docprops' into develop

Adds read/write access to core document properties, those stored in the
/docProps/core.xml package part.
Release v0.2.6
Merge release v0.2.6