RFR: 8279798: Javadoc for BasicTabbedPaneUI is inconsistent

[Alexey Ivanov]

A number of methods in BasicTabbedPaneUI uses the imperative form of the verb in the documentation instead of the third-person form which describes what the method does.

For consistency, I updated such descriptions to use the third-person form of the verb.

I fixed a couple of typos as well.

I also expanded all the wildcard imports into the specific ones.

-------------

Commit messages:
 - Revert the change for assureRectsCreated: it'll be updated in a follow-up issue
 - 8279798: Javadoc for BasicTabbedPaneUI is inconsistent

Changes: https://git.openjdk.java.net/jdk/pull/7031/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=7031&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8279798
  Stats: 63 lines in 1 file changed: 38 ins; 0 del; 25 mod
  Patch: https://git.openjdk.java.net/jdk/pull/7031.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/7031/head:pull/7031

PR: https://git.openjdk.java.net/jdk/pull/7031