Labeling Module: Add the number of injected packets (per attack) to the labels

Add a tag to each attack indicating how many packets that attack injected. For example, notice the new tag with the name injected_packets.

<input>
    <filename>0fadbb2e653e317ebd5c0f164c2b3426.pcap</filename>
    <sha256>f9eb061c19b99a2bbb3e720f8a464229d5e0bca63d2a6fb3ac80f4aef85e6e23</sha256>
</input>
<output>
    <filename>0fadbb2e653e317ebd5c0f164c2b3426_20180913-164729.pcap</filename>
    <sha256>63090e35ec862887248f4f9b6b59fb93a65c3d51fce168ddf4a0c8492dbb182e</sha256>
</output>
<attack>
    <name>PortscanAttack</name>
    <note>This attack used only (random) default parameters.</note>
    <seed>329681334091599541248200642524842105445</seed>
    <timestamp_start>
        <timestamp>1512387989.787456</timestamp>
        <timestamp_hr>2017-12-04 11:46:29.787456</timestamp_hr>
    </timestamp_start>
    <timestamp_end>
        <timestamp>1512388040.8534696</timestamp>
        <timestamp_hr>2017-12-04 11:47:20.853470</timestamp_hr>
    </timestamp_end>
    <injected_packets>1000<\injected_packets>
    <parameters>
        <ip.src user_specified="False">188.165.214.141</ip.src>
        <ip.src.shuffle user_specified="False">False</ip.src.shuffle>
        <mac.src user_specified="False">70:54:d2:19:a5:fe</mac.src>
        <ip.dst user_specified="False">224.0.0.102</ip.dst>
        <mac.dst user_specified="False">01:00:5e:00:00:66</mac.dst>
        <port.dst user_specified="False">[513, 445, 80, 8031, 2003, 993, 22, 8888, 2121]</port.dst>
        <port.open user_specified="False">1</port.open>
        <port.dst.shuffle user_specified="False">False</port.dst.shuffle>
        <port.dst.order-desc user_specified="False">False</port.dst.order-desc>
        <port.src user_specified="False">4514</port.src>
        <port.src.shuffle user_specified="False">False</port.src.shuffle>
        <packets.per-second user_specified="False">38.5</packets.per-second>
        <inject.at-timestamp user_specified="False">1512387989.787456</inject.at-timestamp>
    </parameters>
</attack>

#160 Labeling Module: Add the number of injected packets (per attack) to the labels