Add "trainremote" command

[BillyCheung10botics]

This commit adds a new command "trainremote" that allows users to train their ai model on our AWS server. Currently, the training is hardcoded to train a KerasLinear model with max epoch of 30. You can use this command as the following example shown,

donkey trainremote --tub ~/mycar/data/tub_4_21-06-11/ ~/mycar/data/tub_3_21-06-11/ --path ~/mycar --model modelname 
--url https://hq.robocarstore.com/train/submit_job --get https://hq.robocarstore.com/train/refresh_job_statuses

with mandatory arguments --tub, --path and --model,, and optional arguments --url and --get

• --tub: specify the path(s) of your data tub(s)

• --path: specify the path of your mycar

• --model: specify the file name (without extension) of the resulting model, loss function plot and movie

• --url: the url to post a training request

• --get: the url to get the status of the submitted job

After submitting a job via the "trainremote", the training takes place on our AWS server with a max. duration of 15 min. You can view your submitted job (and others' jobs) on https://hq.robocarstore.com/train/. Usually, the training takes around 10 min to complete, a model file, a plot and a movie are then downloaded from our server, and saved to the folder 'models' and 'movies' respectively.

[DocGarbanzo]

@BillyCheung10botics - this is a great addition. I have three comments:

1. Can you make the —path optional as we have in the train and other commands?
2. Can you please convert print statements to logging?
3. The checks are failing, maybe the package is not available in our conda channels, in that case they should go under pip. Can you check that please?

[DocGarbanzo]

@BillyCheung10botics - can you have a look at addressing the installation issues from the checks above, and a couple of minor comments? It would be great to have that change in Donkey Car.