Compatibility with LineageOS manifest

[jmgao]

At least two bugs here:

• We're not handling ".." in remotes properly
• rejects paths with slashes
• Maybe more?

Example pore.toml snippet that ideally should work:

[[remotes]]
name = 'lineage'
url = 'https://github.com/LineageOS/'
depot = 'android'

[[remotes.project_renames]]
regex = "_"
replacement = "/"

[[remotes.project_renames]]
regex = "^android/"
replacement = ""

[[manifests]]
name = 'lineage'
remote = 'lineage'
project = 'android'