truncating mobile service tables and log continuation token support

This adds support for truncating data in mobile service tables via `azure mobile data truncate` as well as paging though mobile service logs using continuation tokens. 

### azure mobile data truncate

Here is the simple case: 

```
azure mobile data truncate zumocli202 table1
info:    Executing command mobile data truncate
info:    There are 5 data rows in the table.
Do you really want to delete all data from the table? (y/n): y
info:    Deleted 5 rows.
info:    mobile data truncate command OK
```

You can also tell the CLI to go quiet:

```
azure mobile data truncate zumocli202 table1 -q
info:    Executing command mobile data truncate
info:    Deleted 5 rows.
info:    mobile data truncate command OK
```

### paging through logs

Get the first page of the logs and take note of the continuation token:

```
azure mobile log zumocli202 --top 1
info:    Executing command mobile log
data:
data:    timeCreated 2013-01-02T20:15:09.529Z
data:    type warning
data:    source /scheduler/foobar.js
data:    message You are running an empty scheduled job. Update the script for job 'foobar' or disable the job.
data:
data:    Continuation token to receive the next result set: 2520451430904709999-126976e3-caa2-4f27-abf4-d0e8bc840422
info:    mobile log command OK
```

Then use the continuation token to request the subsequent page:

```
azure mobile log zumocli202 --top 1 -c 2520451430904709999-126976e3-caa2-4f27
-abf4-d0e8bc840422
info:    Executing command mobile log
data:
data:    timeCreated 2013-01-02T20:15:09.365Z
data:    type error
data:    source /shared/apnsfeedback.js
data:    message Error in script '/shared/apnsfeedback.js'. Error: ENOENT, open 'C:\DWASFiles\Sites\zumocli202\VirtualDi
rectory0\site\wwwroot\App_Data\config\apnscertificate.p12'
data:
info:    mobile log command OK
```

There is no continuation token in the second invocation of the tool which means this is the end of the logs.