Split handleBasket method into functional pieces

git-svn-id: https://svn.typo3.org/TYPO3v4/Extensions/commerce/branches/55612@83713 735d13b6-9817-0410-8766-e36946ffe9aa
Move initialization of the basket to own method

git-svn-id: https://svn.typo3.org/TYPO3v4/Extensions/commerce/branches/55612@83714 735d13b6-9817-0410-8766-e36946ffe9aa
Rename MYSESSION to sessionData in checkout

git-svn-id: https://svn.typo3.org/TYPO3v4/Extensions/commerce/branches/55612@83719 735d13b6-9817-0410-8766-e36946ffe9aa
Fix canMakeCheckout hook call to use references

git-svn-id: https://svn.typo3.org/TYPO3v4/Extensions/commerce/branches/55612@83721 735d13b6-9817-0410-8766-e36946ffe9aa
Fix cancheckout check for payment to only get processed if finishing the checkout

git-svn-id: https://svn.typo3.org/TYPO3v4/Extensions/commerce/branches/55612@83722 735d13b6-9817-0410-8766-e36946ffe9aa
Fix content empty check

git-svn-id: https://svn.typo3.org/TYPO3v4/Extensions/commerce/branches/55612@83723 735d13b6-9817-0410-8766-e36946ffe9aa
Cleanup unnecessary code

git-svn-id: https://svn.typo3.org/TYPO3v4/Extensions/commerce/branches/55612@83725 735d13b6-9817-0410-8766-e36946ffe9aa