add a better progress bar to read.dcd() and read.ncdf()

[Barry Grant]

Use the txtProgressBar() and setTxtProgressBar() style=3 functions

[Xinqiu Yao]

I have added a progress bar to read.dcd(), however, not yet for read.ncdf() because the latter calls NCDF function get.var.ncdf() to read a block of trajectory frames. Any idea?

[Xinqiu Yao]

Resolved but only for read.dcd. Currently we can't do it for read.ncdf