SongShowPlus importer does not handle verse labels such as 1A

[Phill]

See http://support.openlp.org/issues/1897 for attached song file

*OpenLP Bug Report*
Version: {u'full': u'2.0.1', u'version': u'2.0.1', u'build': None}

--- Details of the Exception. ---

Importing song show plus songs (.sbsong) from jump drive.

 --- Exception Traceback ---
Traceback (most recent call last):
  File "D:\OpenLP_Code\release-2.0.1\build\pyi.win32\OpenLP\out00-PYZ.pyz\openlp.core.ui.wizard", line 188, in onCurrentIdChanged
  File "D:\OpenLP_Code\release-2.0.1\build\pyi.win32\OpenLP\out00-PYZ.pyz\openlp.plugins.songs.forms.songimportform", line 391, in performWizard
  File "D:\OpenLP_Code\release-2.0.1\build\pyi.win32\OpenLP\out00-PYZ.pyz\openlp.plugins.songs.lib.songshowplusimport", line 181, in doImport
  File "D:\OpenLP_Code\release-2.0.1\build\pyi.win32\OpenLP\out00-PYZ.pyz\openlp.plugins.songs.lib.songimport", line 268, in addVerse
ValueError: invalid literal for int() with base 10: '1A'

--- System information ---
Platform: Windows-XP-5.1.2600-SP3

--- Library Versions ---
Python: 2.7.3
Qt4: 4.7.3
Phonon: 4.4.0
PyQt4: 4.8.5
QtWebkit: 533.3
SQLAlchemy: 0.7.7
SQLAlchemy Migrate: 0.7.2
BeautifulSoup: 3.2.1
lxml: 2.3.0
Chardet: 1.0.1
PyEnchant: 1.6.5
PySQLite: 1.0.1
Mako: 0.7.0
pyUNO bridge: -