gitea dump: include version & Check InstallLock

[6543]

close #12757

this way if it is restored and use with an later version it should migrate as usual

close #12759:

[user@PC gitea]$ ./gitea dump -c wrong-conf.ini -f gitea-dump.zip
2020/09/07 19:55:47 ...s/setting/setting.go:522:SetCustomPathAndConf() [W] Using 'custom' directory as relative origin for configuration file: '/home/maddl/git/own/gitea/custom/wrong-conf.ini'
2020/09/07 19:55:47 ...s/setting/setting.go:540:NewContext() [W] Custom config '/home/user/gitea/custom/wrong-conf.ini' not found, ignore this if you're running first time
2020/09/07 19:55:47 ...dules/setting/git.go:91:newGit() [I] Git Version: 2.28.0, Wire Protocol Version 2 Enabled
2020/09/07 19:55:47 cmd/dump.go:190:runDump() [E] Is '/home/user/gitea/custom/wrong-conf.ini' really the right config path?
2020/09/07 19:55:47 main.go:112:main() [F] Failed to run app with [./gitea dump -c wrong-conf.ini -f gitea-dump.zip]: gitea is not initialized

before it just tell the user: Failed to connect to database: Unknown database type:

[codecov-commenter]

Codecov Report

Merging #12760 into master will decrease coverage by 0.00%.
The diff coverage is 38.98%.

@@            Coverage Diff             @@
##           master   #12760      +/-   ##
==========================================
- Coverage   43.30%   43.29%   -0.01%     
==========================================
  Files         648      647       -1     
  Lines       71765    71799      +34     
==========================================
+ Hits        31077    31085       +8     
- Misses      35657    35677      +20     
- Partials     5031     5037       +6     

Impacted Files	Coverage Δ
cmd/dump.go	1.03% <0.00%> (-0.02%)	⬇️
modules/indexer/code/elastic_search.go	0.00% <0.00%> (ø)
modules/indexer/code/indexer.go	35.22% <36.47%> (-0.95%)	⬇️
modules/queue/queue.go	32.25% <47.61%> (+7.86%)	⬆️
models/models.go	57.94% <71.42%> (+0.50%)	⬆️
modules/indexer/stats/db.go	52.17% <0.00%> (-8.70%)	⬇️
modules/charset/charset.go	68.53% <0.00%> (-4.50%)	⬇️
modules/log/event.go	56.60% <0.00%> (-2.84%)	⬇️
services/pull/pull.go	42.03% <0.00%> (+0.46%)	⬆️
modules/git/repo.go	50.76% <0.00%> (+0.50%)	⬆️
... and 4 more

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[6543]

ready to 🚀

[6543]

backport -> #12762