[IMP] runbot: reinforce version

[d-fence]

When updating a bundle and changing the is_base field to True, it creates a new version based on the bundle name. This can potentially breaks builds and moreover, it can breaks the whole runbot when a duplicate version name is created.

With this commit:

• a constraint on the version name uniqueness is added
• the is_base field is hidden in the interface when the bundle name does not match the regular expression defined in the settings
• a version cannot be created by the compute version if the bundle name does not match the above mentioned regular expression