Indicate when a source was added

[nvkelso]

Similar to how we indicate a source was deprecated (for those bad properties that should have been in the other repo).

[nvkelso]

eg: edtf:inception

[stepps00]

Will add these inception dates to each source json in a separate PR shortly:

source,inception
dbpedia.json,2016-05-18
latimes.json,2017-05-11
sdgis.json,2017-01-18
acgov.json,2016-06-29
denvercpd.json,2016-11-17
lbl.json,2017-06-16
se-lant.json,2018-05-03
acme.json,2017-05-04
dial.json,2017-10-09
libraryofcongress.json,2016-05-18
seagv.json,2016-07-25
addr.json,2017-03-08
dk-geodk.json,2018-04-25
lieu.json,2017-07-17
sfac.json,2016-05-04
amsgis.json,2017-01-24
ds.json,2017-10-09
localwiki.json,2017-10-12
sfgov.json,2016-05-04
ar-caba.json,2017-05-24
ebc.json,2017-05-10
mapshaper.json,2015-11-09
sfgov_rbl.json,2017-07-24
atgov.json,2016-05-09
edtf.json,2015-08-20
mapzen.json,2015-11-09
simplegeo.json,2015-12-01
atldpcd.json,2016-12-29
esp-aytomad.json,2017-10-13
mapzenborders.json,2016-05-18
sjp.json,2016-12-15
ausstat.json,2016-09-20
esp-cartobcn.json,2017-10-11
marc.json,2017-10-09
smcgov.json,2016-06-29
austriaod.json,2017-03-20
faa.json,2016-05-18
meso.json,2016-12-08
ssuberlin.json,2017-02-07
azavea.json,2016-10-12
factual.json,2015-09-08
statcan.json,2016-04-14
baltomoit.json,2016-12-20
fifa.json,2017-10-09
minitenders.json,2015-12-15
statoids.json,2017-09-13
bebrus.json,2018-02-21
figov.json,2016-05-24
missing.json,2015-12-15
stpaulgov.json,2017-01-11
begov.json,2016-05-24
fips.json,2016-05-18
mudf.json,2018-04-20
svn-sma.json,2017-04-26
bra.json,2016-09-21
foursquare.json,2016-05-24
name.json,2017-02-27
tgn.json,2016-05-18
btvneighborhoods.json,2016-09-13
fra-odp.json,2017-12-29
naturalearth.json,2015-08-20
thelist.json,2017-05-30
burritojustice.json,2015-12-15
freebase.json,2016-05-18
tkugov.json,2016-11-10
camgov.json,2016-10-03
frgov.json,2016-10-25
no-geonorge.json,2018-04-24
tmpgis.json,2016-11-10
can-abog.json,2017-05-31
gaul.json,2017-10-09
nolagis.json,2016-11-16
torsdfa.json,2017-03-14
can-bbygov.json,2017-03-30
gbr-datalondon.json,2017-12-20
nullisland.json,2015-12-15
transitland.json,2017-04-26
can-calcai.json,2017-05-23
gec.json,2017-10-09
nycgov.json,2016-04-26
uncrt.json,2017-11-15
can-databc.json,2017-12-08
geom.json,2017-02-28
nycgov_dca.json,2017-07-24
unknown.json,2017-02-28
can-dnvgov.json,2017-03-29
geonames.json,2015-08-20
nycgov_dohmh.json,2017-07-24
unlocode.json,2016-03-03
can-edmdsd.json,2017-05-25
nycgov_subway.json,2017-05-03
unsd.json,2017-10-27
can-gatsudd.json,2017-06-13
geoplanet.json,2015-08-20
nytimes.json,2016-05-18
uscensus.json,2016-11-14
can-lvlsu.json,2017-05-04
oakced.json,2016-12-19
uszcta.json,2016-04-08
can-mtlsmvt.json,2017-04-21
hasc.json,2017-02-21
os.json,2016-06-10
vanpds.json,2017-03-27
can-nwds.json,2017-04-03
hkigis.json,2016-11-10
wapo.json,2016-10-21
can-ons.json,2017-06-05
hsgov.json,2016-05-31
osm.json,2017-11-17
whereonearth.json,2015-08-20
can-qcodp.json,2017-06-21
iata.json,2016-05-18
oulugov.json,2016-11-10
whosonfirst.json,2015-12-15
can-rodca.json,2017-06-15
icao.json,2016-05-18
ourairports.json,2015-08-20
wikidata.json,2016-03-07
can-saskodp.json,2017-06-16
ico.json,2017-10-09
wikipedia.json,2015-08-20
can-surgis.json,2017-04-06
ie-gov.json,2018-04-20
outgoing.json,2017-04-11
wmo.json,2017-10-09
can-vicodc.json,2017-06-26
inegi.json,2017-09-06
pedia.json,2016-08-04
woedb.json,2015-12-15
can-wpgppd.json,2017-05-24
iso.json,2017-04-04
porbps.json,2016-10-10
yerbashapes.json,2015-11-09
canvec-hydro.json,2017-05-12
itu.json,2017-10-09
quattroshapes.json,2015-08-20
zetashapes.json,2015-08-20
cbsnl.json,2017-01-31
kuogov.json,2016-11-10
quattroshapes_pg.json,2017-06-08
chgov.json,2016-05-04
lacity.json,2016-09-07
zolk.json,2016-08-22
companieshouse.json,2017-07-27
lacity_oof.json,2017-07-27
santabar.json,2017-10-18