Return guid of newly-created report template to calling function

git-svn-id: svn+ssh://svn.gnucash.org/repo/gnucash/trunk@23077 57a11ea4-9604-0410-9ed3-97b8803252fd
Define 'custom-template' property on report instances (not used yet)

git-svn-id: svn+ssh://svn.gnucash.org/repo/gnucash/trunk@23078 57a11ea4-9604-0410-9ed3-97b8803252fd
New functions to check for custom templates
- whether a report template is a custom one
- whether a report is based on a custom report

git-svn-id: svn+ssh://svn.gnucash.org/repo/gnucash/trunk@23079 57a11ea4-9604-0410-9ed3-97b8803252fd
New function to rename a saved report

git-svn-id: svn+ssh://svn.gnucash.org/repo/gnucash/trunk@23080 57a11ea4-9604-0410-9ed3-97b8803252fd