Monkey configuration: add program options for configuration paths

This patch solves the issue #36.

4 additional program arguments were added for specifying different
configuration files and directories:

-m, --mimes-conf-file # path to monkey.mime
-P, --plugins-conf-dir # path to plugins configuration directory
-l, --plugin-load-conf-file # path to plugins.load file
-S, --sites-conf-dir # path to sites directory

Each option has a default value.

Monkey will try to interpret the options by prepending their values
to default configuration directory. If the obtained path does not
exist, the options will be treated as absolute paths.

I tested using ./configure --prefix=path --plugdir=--path2 and
default build. I was able to load different configuration files
from custom locations with custom names, overriding the default
names which were hardcoded in Monkey.

The patch also contains an unrelated fix to:

bin/monkey --confdir # was not working, while provided by --help

Signed-off-by: Vladimir Cernov <gg.kaspersky@gmail.com>
Merge pull request #123 from kaspersky/systemd

Systemd: add unit file monkey.service
Merge pull request #115 from kaspersky/master

Monkey configuration: add program options for configuration paths
Socket: handle new Kernel 3.14 tcp_autocorking feature.

the server use the TCP_CORK feature to instruct the Kernel to
wait for some data before dispatch it on the socket buffer. This
is a common approach when sending HTTP response headers and then
a content body (file data).

The Linux Kernel 3.14 introduce a new feature called 'tcp autocorking',
it basically do TCP_CORK by default based on specific conditions of
each socket status. This is a good approach to let the Kernel to decide
when it can be used and also it avoid user space to invoke two system
calls to enable/disable the TCP_CORK.

This patch makes the Server to validate if the new feature exists on the
running Kernel and if is enabled, it will disable all manual corking done,
for more details about how it works at Kernel level refer to the following
patch:

    http://goo.gl/AMFIuI

Note: on an older Kernel it will continue working as usual.

Signed-off-by: Eduardo Silva <edsiper@gmail.com>
HTTP: Fix comments' grammar and punctuation in mk_http.c
Merge pull request #125 from TamerTas/master

HTTP: Fix comments' grammar and punctuation in mk_http.c
Removing unnecessary conditionals from src/mk_http.c
Merge pull request #127 from tssavita/http-conditionals

HTTP: Removing unnecessary conditionals from src/mk_http.c