RFR: 7057: Update Copyright year in About dialog and update site landing page

[Guru Hb]

1. Updated Copyright year in About Dialog box to 2020.
2. Update site landing (html) page updated  for : 
    RCP index.html : Banner text (at the top) required padding (similar to IDE update site) 
    Updated Copyright year to 2020.
    Removed JDK 9 entry (as this version is not supported any more) 
    Offline Download entry removed (as They are not hosted). 
    Eclipse 4.8 or later to Eclipse IDE 4.16 or later.

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

Commit messages:
 - 7057: Update Copyright year in About dialog and update site landing page

Changes: https://git.openjdk.java.net/jmc/pull/182/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jmc&pr=182&range=00
  Issue: https://bugs.openjdk.java.net/browse/JMC-7057
  Stats: 40 lines in 6 files changed: 1 ins; 5 del; 34 mod
  Patch: https://git.openjdk.java.net/jmc/pull/182.diff
  Fetch: git fetch https://git.openjdk.java.net/jmc pull/182/head:pull/182

PR: https://git.openjdk.java.net/jmc/pull/182