Update README.postgis

[mwtoews]

I've made many changes to the README.postgis file:

• Use consistent formatting in reStructuredText - some was, some wasn't. To view result, copy/paste the file text into  http://www.tele3.cz/jbar/rest/rest.html
• Wrap lines to 80 columns, trim trailing whitespace, replace tabs with space chars
• Fix typos, and use consistent case and punctuation
• Merged some content from README.raster (I hope); see #1649
• Alphabetize the directory structure
• Add ./libpgcommon to directory structure, and attempt to describe it
• Mention that both Raster and Topology extensions are built by default, add notes how build without them

Other notes:

• There are probably other things that should be improved, such as how to spatially enable a 9.1+ database using extensions
• Could this file be moved back to README? (svn move README.postgis README)
• I'm not sure if mentioning apt-get commands is a great idea, since there are many package managing solutions (yum, etc.), and different distros have different names for these packages (e.g., -devel). I have started (but not completed) UsersWikiInstall to address platform specific instructions (which should probably get mentioned somewhere)

I really don't expect this patch to be applied as-is, since there are probably several improvements to include (or not!).

I've attached both the whole file and a diff patch.

[pracine]

"Python GDAL bindings" is no longer necessary...

[strk]

Splitting the patch into sub-issues would help. I'd love to apply the 80-columns wrap and the reStructuredText cleanup, for example,but wouldn't feel like applying the raster merge in the same commit. Also the rename would need some research on possibly install paths, as I think a long time ago we used to install in the same directory with a lot of other contrib readmes...

[mwtoews]

As suggested, I've limited the scope of this ticket, but regardless, here is a summary of the changes:

• Use consistent formatting in reStructuredText; see formatted result with rst2pdf or rst2html, or if you don't want to install docutils, you can copy/paste the text to  http://www.tele3.cz/jbar/rest/rest.html
• Wrap lines to 80 columns, trim trailing whitespace, replace tabs with space chars
• Fix typos, and use consistent case and punctuation
• Alphabetize the directory structure
• Add ./libpgcommon to directory structure, and attempt to describe it
• Arrange style of REQUIREMENTS section a bit more consistent across components: removing repetition, stating what is required or optional, etc.
• When referencing PostGIS SQL functions, use the "ST_" prefix, where applicable
• Mention that both Raster and Topology extensions are built by default, add notes how build without them

As for renaming to README, I did some digging and I was incorrect—it has always been named README.postgis. Renaming is off-scope.

Both the whole README.postgis file and a diff patch are attached (replacing older files on this ticket).

[strk]

Committed as r9478. It's interesting to note that the instructions for creating an index did not mention "using GiST", see #1680 for a related issue.