pgsql: Move upgrade instructions into its own section under "Server Set

Move upgrade instructions into its own section under "Server Setup and
Operation", merged from upgrade sections in "Installation from Source
Code" and "Backup and Restore". This now gives a single place for all
upgrade information.

Branch
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master

Details
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http://git.postgresql.org/gitweb?p=postgresql.git;a=commitdiff;h=c5ba11f8fb1701441b96a755ea410b96bfe36170

Modified Files
--------------
doc/src/sgml/backup.sgml | 212 ----------------------------
doc/src/sgml/installation.sgml | 158 +---------------------
doc/src/sgml/runtime.sgml | 301 ++++++++++++++++++++++++++++++++++++++++
3 files changed, 304 insertions(+), 367 deletions(-)