doc: clean up overview.rst

[qlyoung]

Move the "how to get" blurb to a more obvious place and include a link
to the apt repo.

Signed-off-by: Quentin Young qlyoung@cumulusnetworks.com

[LabN-CI]

💚 Basic BGPD CI results: SUCCESS, 0 tests failed

Results table

_	_
Result	SUCCESS git pull/4708 5bb7a41 (merge failed)
Date	07/22/2019
Start	22:05:16
Finish	22:26:57
Run-Time	21:41
Total	1815
Pass	1815
Fail	0
Valgrind-Errors	0
Valgrind-Loss	0
Details	vncregress-2019-07-22-22:05:16.txt
Log	autoscript-2019-07-22-22:06:02.log.bz2
Memory	433 387 361
SUCCESS git merge/5357 83621c6	SUCCESS git master a85de97
11/16/2019	07/17/2019
22:05:19	22:05:11
22:31:04	22:26:55
25:45	21:44
1815	1815
1815	1815
0	0
0	0
0	0
vncregress-2019-11-16-22:05:19.txt	vncregress-2019-07-17-22:05:11.txt
autoscript-2019-11-16-22:06:14.log.bz2	autoscript-2019-07-17-22:06:02.log.bz2
410 430 361	431 427 360

For details, please contact louberger

[NetDEF-CI]

Continuous Integration Result: SUCCESSFUL

Congratulations, this patch passed basic tests

Tested-by: NetDEF / OpenSourceRouting.org CI System

CI System Testrun URL: https://ci1.netdef.org/browse/FRR-FRRPULLREQ-9737/

This is a comment from an automated CI system.
For questions and feedback in regards to this CI system, please feel free to email
Martin Winter - mwinter (at) opensourcerouting.org.

<TITLE>clang_check</TITLE>

clang_check

[NetDEF-CI]

Continuous Integration Result: SUCCESSFUL

Congratulations, this patch passed basic tests

Tested-by: NetDEF / OpenSourceRouting.org CI System

CI System Testrun URL: https://ci1.netdef.org/browse/FRR-FRRPULLREQ-9738/

This is a comment from an automated CI system.
For questions and feedback in regards to this CI system, please feel free to email
Martin Winter - mwinter (at) opensourcerouting.org.

<TITLE>clang_check</TITLE>

clang_check