feature #5974 [PropertyInfo] Add Component Documentation (zanderbaldwin)

This PR was merged into the 2.8 branch.

Discussion
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[PropertyInfo] Add Component Documentation

| Q             | A
| ------------- | ---
| Doc fix?      | no
| New docs?     | yes (symfony/symfony#15858)
| Applies to    | `2.8`, `3.0`
| Fixed tickets | N/A

This is still a *work in progress*, but I'd like feedback from anyone regarding structure, grammar and any other improvements while I continue. After speaking with @dunglas, I'm creating a new PR due our branches differing by about 400 commits.

Commits
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a0409d7 Update Reference to Service Container Tags
78ea4a5 Update PropertyAccess Component Path
7b786af Fix Incorrect Indent
96b139b Suggested Changes
cf7a0ea Add PropertyInfo Component Documentation

Author: weaverryan