Added optional use of readline library for shell_tui

[ErjanAltena]

I have added optional usage of the readline library in shell tui. With this addition there can be scrolled though previous entered commands with the up/down arrow keys and tab completion on commands is added.

Note that this the GNU readline library has a GPL license and therefore the usage is optional.

Regards,
Erjan Altena

[coveralls]

Coverage remained the same at 73.571% when pulling d47f924 on ErjanAltena:develop into d62731a on apache:develop.

[coveralls]

Coverage remained the same at 73.571% when pulling d47f924 on ErjanAltena:develop into d62731a on apache:develop.

[coveralls]

Coverage remained the same at 73.571% when pulling e177d2a on ErjanAltena:develop into d62731a on apache:develop.

[coveralls]

Coverage remained the same at 73.571% when pulling e177d2a on ErjanAltena:develop into d62731a on apache:develop.

[pnoltes]

Hi Erjan,

Although I do like functionality added, I am not sure if this can be accepted to Celix.

First of IANAL. But if I am correct, by adding a GPL piece of code or dependency you are creating a 'derivative work' of the GPL code and the GPL requires that all 'derivative work' should be shared. If this feature is enabled, this then also holds for all Celix users.

With LGPL this is only true for code based on the LGPL code, not for code which only uses the LGPL code (e.g. use the LGPL part as as a shared lib dependency).

The (core) Celix framework is currently only dependent on the libc, uuid, curl and zlib. For linux, if I am correct, this means:

• glibc (LGPL)
• libuuid (BSD, from util-linux)
• zlib (zlib license, permissive license)
• libcurl (MIT/X)

Note that these are permissive licenses or LGPL. Although it would be nice to completely avoid the LGPL dependencies this is not always feasible.

If you like, we can discuss this further on the celix dev mailling list. But for now I cannot accept this pull request.

Pepijn

[ErjanAltena]

SInce I understand the legal issues with using a GPL licensed library I will close this pull request. I think it will not be too difficult to browse though the history without using an external library. I will look into that.